// 简易版：从身份证解析出生日期（支持15/18位），并将公历转为农历（1900-2099）。

// 每年信息：位标记月大小和闰月信息（1900-2099）
// 数据来源于已公开的农历换算算法资料，覆盖范围内适用。
const lunarInfo: number[] = [
  0x04bd8, 0x04ae0, 0x0a570, 0x054d5, 0x0d260, 0x0d950, 0x16554, 0x056a0, 0x09ad0, 0x055d2,
  0x04ae0, 0x0a5b6, 0x0a4d0, 0x0d250, 0x1d255, 0x0b540, 0x0d6a0, 0x0ada2, 0x095b0, 0x14977,
  0x04970, 0x0a4b0, 0x0b4b5, 0x06a50, 0x06d40, 0x1ab54, 0x02b60, 0x09570, 0x052f2, 0x04970,
  0x06566, 0x0d4a0, 0x0ea50, 0x06e95, 0x05ad0, 0x02b60, 0x186e3, 0x092e0, 0x1c8d7, 0x0c950,
  0x0d4a0, 0x1d8a6, 0x0b550, 0x056a0, 0x1a5b4, 0x025d0, 0x092d0, 0x0d2b2, 0x0a950, 0x0b557,
  0x06ca0, 0x0b550, 0x15355, 0x04da0, 0x0a5d0, 0x14573, 0x052d0, 0x0a9a8, 0x0e950, 0x06aa0,
  0x0aea6, 0x0ab50, 0x04b60, 0x0aae4, 0x0a570, 0x05260, 0x0f263, 0x0d950, 0x05b57, 0x056a0,
  0x096d0, 0x04dd5, 0x04ad0, 0x0a4d0, 0x0d4d4, 0x0d250, 0x0d558, 0x0b540, 0x0b5a0, 0x195a6,
  0x095b0, 0x049b0, 0x0a974, 0x0a4b0, 0x0b27a, 0x06a50, 0x06d40, 0x0af46, 0x0ab60, 0x09570,
  0x04af5, 0x04970, 0x064b0, 0x074a3, 0x0ea50, 0x06b58, 0x05ac0, 0x0ab60, 0x096d5, 0x092e0,
  0x0c960, 0x0d954, 0x0d4a0, 0x0da50, 0x07552, 0x056a0, 0x0abb7, 0x025d0, 0x092d0, 0x0cab5,
  0x0a950, 0x0b4a0, 0x0baa4, 0x0ad50, 0x055d9, 0x04ba0, 0x0a5b0, 0x15176, 0x052b0, 0x0a930,
  0x07954, 0x06aa0, 0x0ad50, 0x05b52, 0x04b60, 0x0a6e6, 0x0a4e0, 0x0d260, 0x0ea65, 0x0d530,
  0x05aa0, 0x076a3, 0x096d0, 0x04afb, 0x04ad0, 0x0a4d0, 0x1d0b6, 0x0d250, 0x0d520, 0x0dd45,
  0x0b5a0, 0x056d0, 0x055b2, 0x049b0, 0x0a577, 0x0a4b0, 0x0aa50, 0x1b255, 0x06d20, 0x0ada0,
  0x14b63, 0x09370, 0x049f8, 0x04970, 0x064b0, 0x168a6, 0x0ea50, 0x06b20, 0x1a6c4, 0x0aae0,
  0x092e0, 0x0d2e3, 0x0c960, 0x0d557, 0x0d4a0, 0x0da50, 0x05d55, 0x056a0, 0x0a6d0, 0x055d4,
  0x052d0, 0x0a9b8, 0x0a950, 0x0b4a0, 0x0b6a6, 0x0ad50, 0x055a0, 0x0aba4, 0x0a5b0, 0x052b0,
  0x0b273, 0x06930, 0x07337, 0x06aa0, 0x0ad50, 0x14b55, 0x04b60, 0x0a570, 0x054e4, 0x0d160,
  0x0e968, 0x0d520, 0x0daa0, 0x16aa6, 0x056d0, 0x04ae0, 0x0a9d4, 0x0a2d0, 0x0d150, 0x0f252,
  0x0d520
];

function li(y: number): number {
  const idx = y - 1900;
  const v = lunarInfo[idx];
  if (v === undefined) {
    throw new Error(`Year out of supported range: ${y}`);
  }
  return v;
}

function lYearDays(y: number): number {
  let i, sum = 348;
  const info = li(y);
  for (i = 0x8000; i > 0x8; i >>= 1) sum += (info & i) ? 1 : 0;
  return sum + leapDays(y);
}

function leapMonth(y: number): number {
  return li(y) & 0xf;
}

function leapDays(y: number): number {
  if (leapMonth(y)) return (li(y) & 0x10000) ? 30 : 29;
  return 0;
}

function monthDays(y: number, m: number): number {
  return (li(y) & (0x10000 >> m)) ? 30 : 29;
}

function diffDays(date1: Date, date2: Date): number {
  const t1 = Date.UTC(date1.getFullYear(), date1.getMonth(), date1.getDate());
  const t2 = Date.UTC(date2.getFullYear(), date2.getMonth(), date2.getDate());
  return Math.floor((t1 - t2) / 86400000);
}

export function solarToLunar(date: Date): { year: number; month: number; day: number } {
  const baseDate = new Date(1900, 0, 31); // 1900-01-31
  let offset = diffDays(date, baseDate);
  if (offset < 0) throw new Error('Date out of range (before 1900-01-31)');

  let lunarYear = 1900;
  let daysInYear = lYearDays(lunarYear);
  while (offset >= daysInYear && lunarYear < 2100) {
    offset -= daysInYear;
    lunarYear++;
    daysInYear = lYearDays(lunarYear);
  }

  let leap = leapMonth(lunarYear);
  let isLeap = false;
  let lunarMonth = 1;
  let daysInMonth: number;
  while (true) {
    if (leap > 0 && lunarMonth === leap + 1 && !isLeap) {
      isLeap = true;
      daysInMonth = leapDays(lunarYear);
    } else {
      daysInMonth = monthDays(lunarYear, lunarMonth);
    }
    if (offset < daysInMonth) break;
    offset -= daysInMonth;
    if (isLeap && lunarMonth === leap + 1) isLeap = false;
    else lunarMonth++;
  }
  const lunarDay = offset + 1;
  return { year: lunarYear, month: lunarMonth, day: lunarDay };
}

export function pad2(n: number): string { return n < 10 ? `0${n}` : String(n); }

export function solarToLunarString(dateStr: string): string {
  const d = new Date(dateStr);
  if (isNaN(d.getTime())) return '';
  try {
    const l = solarToLunar(d);
    return `${l.year}-${pad2(l.month)}-${pad2(l.day)}`;
  } catch {
    return '';
  }
}

export function parseBirthFromIdCard(id: string): string | null {
  if (!id) return null;
  const s = id.trim();
  if (s.length === 18) {
    const y = s.slice(6, 10);
    const m = s.slice(10, 12);
    const d = s.slice(12, 14);
    const str = `${y}-${m}-${d}`;
    const date = new Date(str);
    if (date.getFullYear() === +y && (date.getMonth() + 1) === +m && date.getDate() === +d) {
      return str;
    }
    return null;
  }
  if (s.length === 15) {
    const y = `19${s.slice(6, 8)}`;
    const m = s.slice(8, 10);
    const d = s.slice(10, 12);
    const str = `${y}-${m}-${d}`;
    const date = new Date(str);
    if (date.getFullYear() === +y && (date.getMonth() + 1) === +m && date.getDate() === +d) {
      return str;
    }
    return null;
  }
  return null;
}
